The presence of radon gas in residences and commercial buildings is now recognized as a health threat. Accordingly, significant commercial effort is dedicated to the fabrication and installation of systems for eliminating or removing radon gas from new and existing buildings.
It is generally recognized that radon is generated by decaying radium in the ground beneath buildings. Radon enters buildings through the floors or walls of their basements. Because of increasing efforts to conserve heating and cooling energy, many newer homes and buildings are relatively airtight. Such homes and buildings are particularly likely to contain unacceptable concentrations of radon.
Radon can be removed by venting a building's basement to the external atmosphere. Such venting is often facilitated by a fan, pump, or blower which is positioned to create a slightly negative pressure in the basement in comparison to the pressure of the atmosphere outside the building. This provides continuous removal of radon and other gases from the basement.
Rather than venting the basement itself, many radon evacuation systems are connected to vent gases from ground regions under the basement floor, rather than from the basement itself. Such systems are generally preferable since less air transfer is required. Furthermore, these systems vent the radon before it can enter the building.
It is relatively easy to provide for radon removal during construction of a home or commercial building. However, it has become necessary to retrofit existing structures with systems for eliminating the presence of radon. In fact, the design and installation of radon elimination systems for connection to underfloor ground regions of existing buildings has become a significant commercial activity. Nevertheless, determining the parameters of such radon elimination systems is largely a matter of guesswork. Accordingly, many systems provide much more capacity than actually needed. While this has no adverse effect on radon removal, the costs of operating an over-sized radon evacuation system can be very significant--especially in large commercial buildings. Accordingly, there is a need for devices and procedures for correctly sizing the components of radon removal systems.
Current underfloor radon removal systems typically comprise a blower or pump which is connected through one or more vent holes in a basement floor to underfloor ground regions beneath a building. Such vent holes typically have diameters in the range of about four inches. The number of vent holes is mandated by the available air or fluid communication beneath the basement floor. In some cases, a single, centrally-located vent hole may be sufficient to create a negative pressure (with regard to the building interior) beneath an entire basement floor. In other cases, underfloor features may prevent air or pressure communication between the location of the vent hole and other locations. Accordingly, multiple vent holes must be provided to create a negative pressure beneath the entire building floor. Testing must be conducted to determine the number of required vent holes.
Current testing methods involve drilling a number of test holes at various locations around a basement floor. Test holes are typically about three-eighths of an inch in diameter. Testing proceeds by first connecting a vacuum test source such as a pump or blower to a single larger vent hole. All other vent holes and test holes are sealed. The vacuum test source typically comprises a general-purpose shop-type vacuum cleaner or some other type of blower which operates at a fixed capacity.
A very sensitive pressure measuring or vacuum sensing device is then used to determine whether the vacuum test source is creating a negative pressure in nearby test holes (the terms "vacuum" and "negative pressure" are used in this document to indicate pressures below ambient or atmospheric pressure). If the vacuum test source does not create a vacuum or negative pressure in a particular test hole, an additional vent hole is provided in closer proximity to that particular test hole and the vacuum test source is connected to the additional vent hole to determine whether it will provide the needed negative pressure at the test hole. This testing continues, with additional vent holes being provided as needed so that each test hole is subjected to a negative pressure by at least one of the vent holes.
The procedure described above results in one or more vent holes which must be connected in parallel to a permanently-installed vacuum source. The permanently-installed vacuum source must be sized to subject all vent holes, simultaneously, to enough vacuum to put the entire underfloor region under a negative pressure with respect to the internal air pressure of the building. Currently, specifying the capacity of the permanently-installed vacuum source is done mostly by guesswork. Accordingly, the permanently-installed vacuum source is usually grossly oversized. In a large commercial building, the power consumed by the permanently-installed vacuum source is a significant expense. Therefore, it would be desirable to provide a permanently-installed vacuum source in a radon removal system which has a capacity of no more than is actually needed to provide a negative pressure at all underfloor areas.
The invention described below comprises methods and apparatus which can be used to determine the actual pressure and volume requirements of a permanently-installed vacuum source in a radon removal system such as described above.